The present invention relates to detecting the acidity or alkalinity of soil. More particularly, it relates to methods and devises for automatically collecting data on the acidity or alkalinity of soil at a number of places in a field.
Site-specific farming, or precision farming, is used today in order to improve crop yields, lower costs, and to protect the environment, by treating different parts of a given field according to their specific conditions, instead of treating the entire field according to the average conditions throughout. In this way, for example, lime can be applied only to areas of a field which have overly acidic soil, which reduces the costs of materials and labor, and avoids excessively alkaline soil from unnecessary liming.
Typically, data on soil properties, including pH, are gathered by collecting a number of soil samples and analyzing them in a laboratory. The standard laboratory pH test for a single soil sample requires mixing equal masses of de-ionized water and soil, stirring vigorously for five to ten seconds, letting the mixture stand for ten to thirty minutes, and measuring the pH of the slurry using a calibrated pH meter. This process must be repeated for each sample. Furthermore, each sample must be individually packaged to keep it from being contaminated during transport from the field to the laboratory, and labeled or otherwise identified with the specific location from which it was collected.
Because of the difficulty and expense of collecting and analyzing samples in the field with laboratory analysis, the total number of samples that can feasibly be collected is limited. Consequently, the resolution of the data is limited, so that current methods generally produce values of soil properties for areas on the order of a hectare.
As will be appreciated by persons of ordinary skill in the art, soil pH may have significant variation within a field. Some fields have soil pH ranging from 5 to 8, with a coefficient of variation exceeding 10%. Combining soil samples over an area of 1 ha leads to a loss of information about spatial variability, and doubts exist about the accuracy of interpolated maps from grid soil sample data. Therefore, persons of ordinary skill in the art will recognize that the variation in soil pH over the area of a single grid can greatly exceed the experimental error in measuring soil pH. The accuracy with which processes such as liming, which are indicated based at least in part on soil pH, can be prescribed is restricted primarily by sampling density. Consequently, crop productivity as a whole is restricted by sampling density. Thus, there is an ongoing need to develop systems and methods to decrease the cost of soil sampling and to improve the resolution of soil property maps. The present invention is directed toward meeting this need.
The present invention relates to a method and apparatus for automatically measuring soil pH in the field. An apparatus is disclosed, suitable for a standard tractor to tow, which will automatically measure soil pH at a relatively large number of places throughout a field. Also disclosed is an apparatus for automatically measuring the soil pH at a relatively large number of places throughout a field, including a devise for simultaneously measuring the position of the apparatus, in order to automatically create a soil pH map.
In one form of the invention, an apparatus for automatically measuring the pH of soil at a relatively large number of places in the field is disclosed, comprising a chassis suitable for towing by a standard tractor; a plurality of wheels; a tank for holding water; a compressed air tank; at least one shank for exposing the soil at the desired sampling depth; at least one pH sensor, each including at least one probe; a probe assembly for each probe, including a sampling platform for collecting soil from pre-selected soil depths and bringing it into contact with the probe, an actuator for moving the sampling platform between an extended position in which a soil sample is collected and a retracted position in which the soil sample is in contact with the probe, and one or more nozzles connected by hoses to the tanks of water for cleaning the probe between measurements by directing water onto it; and an onboard computer for collecting and storing the data.
Another form of the invention includes an apparatus for automatically creating a map of the pH of soil in a field, comprising an apparatus for automatically measuring the pH of soil at a relatively large number of places in the field, and a sensor for continuously detecting the position of the apparatus to allow each pH measurement to be automatically recorded in conjunction with the location of the soil which was measured.
Another form of the invention includes a method for measuring the pH of the soil at a relatively large number of places throughout a field, comprising: providing an apparatus for automatically measuring the pH of soil at a relatively large number of places in the field, including a chassis suitable for towing by a standard tractor, a plurality of wheels, a tank for holding water, a compressed air tank, at least one shank for exposing soil at the desired sampling depth, at least one pH sensor, each including a probe, a probe assembly for each probe including a shank for controlling the location of the probe assembly relative to the surface of the ground, a sampling platform for collecting soil from pre-selected soil depths and bringing it into contact with the probe, an actuator for moving the sampling platform between an extended position in which a soil sample is collected and a retracted position in which the soil sample is in contact with the probe, and one or more nozzles connected to a reservoir of water for cleaning the probe between measurements by directing water onto it, and an onboard computer for collecting and storing the data; selecting a depth at which soil pH measurements will be made; selecting a speed corresponding to the desired distance between locations for pH measurements; and towing the chassis through the field at the selected speed to collect data for a number of places throughout it.
Another form of the invention includes a method for creating a relatively high resolution pH map for a field, comprising: providing an apparatus for automatically creating a map of the pH of soil in a field; selecting a depth at which soil pH measurements will be made; selecting a speed corresponding to the desired distance between locations for pH measurements; and towing the chassis through the field at the selected speed to collect data for a number of places throughout it.
One object of the present invention is to provide a unique apparatus for creating relatively high resolution pH maps. Other objects and advantages of the present invention will be apparent from the following description.